1. Field of the Invention
This invention relates to a video tape recorder (VTR) capable of recording and reproducing any of plural signals largely different in frequency bands including narrow band signals such as NTSC signals and wide band signals such as high definition television .signals for presenting more definite images than NTSC.
2. Description of the Prior Art
A method for recording and reproducing the conventional signals having a frequency band of about 4 to 5 MHz such as NTSC signal and PAL signal and signals for presenting more definite images, for example, high definition signals (HD signals) and signals called HDMAC proposed in Europe, having a wide frequency band of about 8 to 20 MHz which is two to five times that of the NTSC signal, all by one VTR was disclosed in the U.S. Pat. No. 4,730,222. This method was designed to detect whether the input signals were the narrow band signals like the conventional NTSC signals or the wide band signals like the HD signals, and increase the rotating speed of the cylinder, for example, two times for wide band signals and double the running speed of the tape, thereby to enlarge the capacity of the electromagnetic converting system twice as much as that of narrow band signals, thereby enabling to record and reproduce the wide band signals. In other words, this method was to increase the rotating speed of the cylinder and running speed of the tape in proportion to the input signal band.
The method, however, had two problems. One thing was that, when the band of the wide band signal became two to five times as wide as the conventional signal, it was necessary to accelerate the rotating speed of cylinder, running speed of tape and the FM carrier frequency individually 2 to 5 times, so that it was difficult to obtain satisfactory performances in the electromagnetic converting system such as abrasion property of the head, head efficiently and noise caused by head rubbing. The other problem was that the recording time was reduced in reverse proportion to the running speed of the tape, which was a serious problem in a VTR.